Tagged: psychrometric calculator
- November 27, 2015 at 12:07 pm #5109
Air conditioning systems are very important part among the energy consuming building systems. Strict requirements to the IAQ (Indoor Air Quality) make the energy consumption more significant.
It is clear that the rational choice of the thermodynamic processes for the air treatment makes it cheaper to operate through the life of the equipment.
The design process is to calculate the number of processing circuits of the air handling unit (AHU) and to thoroughly shake out the alternatives. As usual there are different ways that a designer can reduce the total life-cycle costs.
Scheme may differ from each other as the set of processing elements and their sequence. Of course, iteration number depends on the complexity of the case and the engineer’s qualification. But even for the most experienced designer it will be useful to calculate two – three additional options.
Here comes an example of two circuits for identical purposes with different energy consumption. The example is: air handling unit with recirculation for “clean room” IAQ – DB=20°С and relative humidity =45% and air flow = 20,000 m3/h
Weather design conditions: DB=35°С and relative humidity =60%
The first scheme: cooling load – 157.7 kW, heating load – 79.3 kW
The second scheme (smart): cooling load – 87.7 kW, heating load – 15.9 kW.
This faithful approach is linked to the costs of expensive designer’s time. It comes to specify thermodynamic processes on psychrometric chart, to extract from the chart (not exactly) air properties for each process (dry bulb temperature, wet bulb temperature, dew point temperature, absolute humidity, enthalpy, relative humidity), to calculate cooling loads, heating loads, coolant flow, water and power for each treatment process.
A rational approach is to pass on to the computer time-consuming processes associated with the psychrometric chart and calculations by the formulas and to direct engineer’s intelligence to analysis and the creation of “smart” circuits.
“Online AHU calculator” allows engineer to spend about 3 minutes on each psychrometric calculation (including data entry). The tool is designed for experienced engineers and beginners. For students I’d advise to use it only for testing – the traditional method should be used to learn. There are enough elements of handling equipment in palette to use in AHU any thermodynamic process:
– sensible heating / cooling,
– cooling and dehumidification (coil or evaporative equipment),
– heating and humidification (air washer or wet pad),
– isothermal humidification (steam),
– adiabatic humidification (air washer or wet pad),
– adiabatic mixing of air,
– isothermal dehumidification (desiccant).
Registered users have a number of advantages:
– their calculations are stored on the site and the user has the opportunity to return to the calculation and repeat it after minor changes or without them,
– registered users pay less,
– registered users can to appeal to a professional board administrator.
- November 30, 2015 at 7:17 am #5114
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